Rotating shroud



June 25, 1963 E. P. WARNKEN 3,095,138

RQTATING SHROUD Original Filed May 28, 1957 5 Sheets-Sheet 1 INVENTOR. ELMER R WARN/TEN Fl BY A1 L QM w SM June 25, 1963 E. P. WARNKEN ROTATING SHROUD 3 Sheets-Sheet 2 Original Filed May 28, 1957 INVENTOR. ELMER I? WARN/(EN June 25, 1963 E. P. WARNKEN 3,095,138

ROTATING SHROUD Original Filed May 28, 1957 3 Sheets-Sheet s F 1 7. v M AZ P" if] 15. 4,

Fig. 5.

INVENTOR. E 1. MER R WARN/(EN 3,095,138 ROTATING SHROUD Elmer P. Warnken, Cincinnati, Ohio, assignor, by mesne assignments, to Studebaker Corporation, South Bend,

a corporation of Michigan Original application May 28, 1957, Ser. No. 662,229, new Patent No. 2,952,442, dated Sept. 13, 1960. Divided and this application Apr. 4, 1960, Ser. No. 19,686

Claims. (Cl. 230134) This invention relates to shrouds for securing and rigidifying the outer ends of a row of blades in a rotor for an aircraft engine, or the like. This is a division of my copending application Serial No. 662,229, filed May 28, 1327, now Patent No. 2,952,442, issued September 13,

Rotor blades have a tendency to gain or lose tip angle when of substantial size, especially length, and when rotating at high speeds; therefore, it is an object of this invention to provide a shroud that will so secure and rigidity the tips of the blades that the proper tip angle is main tained in operation.

A further object of this invention is to provide a shroud which controls the tip amplitude during flight conditions to reduce the tendency toward blade deflection and to minimize vibration of the rotor blades.

A further object of this invention is to provide a rotor shroud which ties together the blades in a row to allow every blade in the row to accept its share of mechanical loads which develop during rotating stall of the blades, i.e., when only a portion of the blades are in aero-dynamic stall.

A further object of this invention is to provide a rotor shroud which maintains a minimum tip clearance between rotating portions of the compressor and the casing thereof, and thereby minimizes recirculation of air around the tips of the blades.

A further object of this invention is to provide a lightweight segmental shroud that can be readily assembled with rotor blades.

A further object of this invention is to provide a shroud which is mounted on but not attached to the rotor blades and in which bushings in the shroud are provided with radial slots into which tips of the rotor blades fit so that 'the shroud can expand or contract with respect to the blades without causing buckling of the blades or shroud. A further object of this invention is to provide a shroud which is held together by a continuous winding which accepts the load imposed by rapid rotation.

A further object of this invention is to provide a segmental shroud baving outwardly projecting channelshaped segments mounted on the tips of the blades, the segments forming an air-seal with the casing of the rotor,

the segments being held together by a resin-impregnated winding of substantially continuous glass fibre rovings, or the like, wound between the flanges of the channel-shaped segments and bound by the resin.

The above and other objects and features of the invention will in part be apparent and will in part be obvious to those of ordinary skill in the art to which this in vention pertains from the following detailed description, and the drawings, in which:

FIGURE 1 is a fragmentary view in transverse section of a portion of the air compressor section of a jet aircraft engine provided with rotor 'biade shrouds constructed in accordance with an embodiment of this invention;

FIG. 2 is a fragmentary view of a portion of the rotor blades and rotor shroud of one row of rotor blades;

FIG. 3 is a view in section taken on a line III-III in FIG. 2;

FIG. 4 is a fragmentary exploded view of the rotor shroud and one blade of the rotor;

3,d-95,l3'8 Patented June 25, 1963 FIG. 5 is a view in side elevation of a blade tip bush- FIG. 6 is a view in elevation showing the interior of a fragmentary portion of a shroud of a rotor constructed in accordance with another embodiment of this invention;

FIG. 7 is a view in section of the shroud illustrated in FIG. 6 and of a portion of a device for making the shroud, the section being taken on the line VIIVII in FIG. 6; and

FIG. 8 is a view in section of the shroud taken along the line VIII-VIII in FIG. '6, a portion of one blade being shown in association therewith.

In FIGURE 1 a portion of the compressor section 10 of a jet aircraft engine is illustrated. The compressor section includes an outer casing 12 in which stator blades 13 are mounted. Within the casing is a rotor 14 provided with rows of rotor blades 16.

As indicated in FIG. 2, a plurality of blades 16 comprises a row. The outer ends of the blades 16 of each row are secured to a rotating shroud 17. As shown in FIG. 4, the shroud '17 includes a plurality of blade-receiving channel-shaped segments 18 forming a ring or shell and a plurality of hoop-receiving channel-shaped segments 19 forming a second ring or shell. The segments 18 and 19 are formed of resin-impregnated fibre glass cloth molded to channel shape, as shown. The angle subtended by each segment may be of any desired size, but preferably is degrees or less, but may be any size up to 360 degrees. Preferably, the bladereceiving segments 18 are short segments, each of which receives the end of one blade, and the hoop-receiving segments 19 are approximately 60 degree segments. The segments 19 are slightly narrower than the segments 18, as indicated in FIG. 3 and are received between flanges 21 and 22 of the blade-receiving segments.

The rows of segments are separated by a cellular member or honeycomb 23 of perforated, lightweight, rigid material, such as resin-impregnated fibre glass or perforated aluminum of light weight but sufliciently rigid to maintain the segment rings separated when the rotor rotates at high speed. Preferably, the honeycomb is formed of aluminum which has cut away portions or perforations to give it light weight of the order of approximately eight pounds per cubic foot.

The segments of the blade-receiving ring are provided with slots 26 in which bushings 27 are received. Each of the bushings 27, as shown in FIG. 3, is provided with a relatively deep slot 28 in which the tip of one of the blades 16 is received. In addition, each bushing is provided with an annular slot or groove 29 in which the edges of the segment are received. As shown, the outer face 31 of the bushing conforms in shape to and engages the outer segment v19. The bushings may be formed of a hard, stiff, durable plastic material, such as nylon or Teflon. The honeycomb is also provided with a slot 32 of suflicient size to receive the bushing. The honeycomb thereby aids in holding the bushing in place.

The blade-receiving slot of each bushing extends sub stantially radially of the shroud segments, and the tips of the blades are slidably received in the slots of the bushings.

The segments are cemented together and to the honeycomb material. As shown in FIG. 3, the edges 33 and 34 of the flanges of the segment rings 18 and 19 are substantially aligned. As shown in FIG. '1, the shroud is received in a slot 35 in the inner face of the casing, and the edges of the flanges of the segment rings are very closely spaced from the base of the slot 35 to form an air-seal between the rotating elements and the casing. The contour of the inner faces of the segments 18 is shown as a substantially smooth curve, but the contour may be 3 varied, particularly at the area adjacent the slots 26 as required to give a proper aerodynamic shape.

The segments of the shroud are reinforced and held together by a retaining winding 36 of elongated fibres of resin-impregnated glass, or the like. Winding'36 comprises many turns on the segments in the space between the flanges of the channels. Preferably, as shown in FIG. 3, the thickness of the winding is less than the depth of the flanges 37 of the hoop-receiving segments so that a short air gap G between the winding 36 and the casing 12 will be formed, as shown in FIG. 1. The winding may be made with fibre glass rovings impregnated with a suitable resin such as an epoxy resin or a phenolformaldehyde resin. The rovings are wound numerous times around the segment rings to provide a substantially continuous winding or hoop of great strength which holds the seg ments firmly in assembled relation.

If desired, all portions of the shroud may be formed of metal, and the winding may be formed of stainless steel wire, or the like. When steel wire is used for the winding, adjacent convolutions may be locked together by an appropriate solder, such as silver solder, or the like. The solder may be applied to the wire before it is wound, and, then, after the rotor has been wound, the rotor may be heated to cause fusion of the solder to tightly grip the wire and hold it in place.

When the rotor is in operation, the shroud may expand slightly because of centrifugal force, and, as it expands, the bushings can slide outwardly of the blade tips without causing distort-ion of the blades or of the shroud.

In FIGS. 6-8 inclusive is shown a shroud 41 constructed in accordance with another embodiment of this invention. The shroud 41 includes a central strip or annular shell 42 which may be formed of strong, durable, resilient material such as one of the plastic materials, such as nylon and Teflon. Surrounding the strip 42 is a ring or retaining band 43 made up of a filamentary winding which may be formed of elongated, resin-impregnated, glass fibres or other suitable filamentary material. The winding ring 43 is formed on a mandrel 44 (FIG. 7) which may be generally cylindrical and has an annular shoulder 46. A ring 47 slides on one end of the mandrel and co-operates with the shoulder 46 to form an annular slot in which the winding is formed.

The central strip 42 may be formed flat. A plurality of equally spaced sockets 48 are formed in the central strip. The central strip is wound around the mandrel 44, the central strip being just long enough to form a complete ring. Then the resin-impregnated filamentary material is wound in the slot surrounding the strip 42. The assembly may be heated to set the resin to hold the filamentary material in place. Then the ring 47 and the assembly are slid off the mandrel 44 and the resin may be cured in the usual manner to form the completed shroud 41. The shroud 41 is mounted on blades 49, only one of which is shown, in the manner indicated in FIG. 8. Each blade 49 is provided with a tang 51 at the outer end thereof. The tang 51 fits in and is slidably received in one of the sockets 48.

The shroud illustrated in FIGS. 6-8 inclusive operates in the same manner as described earlier. As shown, the edges of sockets extend substantially radially, so that, as the shroud expands slightly during operation, the shroud can move out or in along tangs 51, while the shroud holds the blades in proper position.

It will be apparent to those skilled in the art to which this invention pertains, that the illustrated embodiments may be modified or changed without departing from the spirit and scope of the appended claims.

Therefore, what I claim as new and desire to secure by Letters Patent is:

1. A shroudfor a row of rotor blades which comprises a ring composed of a plurality of arcuate blade-receiving segments having on their periphery outwardly facing flanges thereby forming a continuous annular channel, said arcuate segments having radially extending sockets for receiving the tips of the blades in a row of rotor blades with the tips of the blades being slidable lengthwise of the sockets, a second plurality of arcuate segments outboard of the blade tips and located between and spanning the flanges of the blade-receiving segments, the segments of the second plurality forming a ring, a relatively stiff filler member in the space between the segment rings and surrounding tips of the blades, and a substantially continuous winding of resin-impregnated filamentary material forming a retaining band embracing the segments of the second plurality to hold the segments together.

2. A shroud in accordance with claim 1 having a guide bushing disposed in each socket, the bushing engaging one of the blade-receiving segments adjacent the edge of the socket thereof, the bushing having a radially extending socket for receiving the tip of a blade, the filler embracing the guide bushing.

3. A shroud in accordance with claim 2, characterized by the fact that an outer face of each bushing is engaged by one of the segments of the second plurality.

4. A shroud for a row of rotor blades which comprises a plurality of arcuate blade-receiving segments of outwardly facing channel-shape in cross section having spaced flanges forming a ring, the blade-receiving segments being provided with radially extending sockets in which the tips of the blades are received with the tips of the blades being slideable lengthwise of the sockets, a second plurality of arcuate segments of outwardly facing channel shape in cross section received between and spanning the flanges of the blade-receiving segments and-forming a ring, a stiff filler in the space between the segments surrounding the tips of the blades, and a substantially continuous winding of resin-impregnated'glass fibre rovings forming a retaining band surrounding the segments of the second plurality to hold the segments together.

5. A rotor which comprises a shaft, a plurality of rotor blades mounted on said shaft and a shroud for said blades, said shroud comprising a plurality of arcuate blade receiving segments of outwardly facing channel shape forming a ring, the segments having spaced flanges, there being radially extending sockets in said blade-receiving segments receiving the tips of the blades, a second plurality of arcuate segments of outwardly facing channel shape received between and spanning the flanges of the inner segments outboard of the tips of the blades to form a second ring, a stiff filler in the space between the segments and surrounding the tips of the blades, and a substantially continuous winding of resin-impregnated glass fibre rovings forming a retaining band surrounding the segments of the second plurality to hold the segments together, the tips of the rotor blades being slideable lengthwise of the sockets, whereby the shroud may expand and contract independently of the rotor blades.

' References Cited in the file of this patent UNITED STATES PATENTS 

1. A SHROUD FOR A ROW OF ROTOR BLADES WHICH COMPRISES A RING COMPOSED OF A PLURALITY OF ARCUATE BLADE-RECEIVING SEGMENTS HAVING ON THEIR PERIPHERY OUTWARDLY FACING FLANGES THEREBY FORMING A CONTINUOUS ANNULAR CHANNEL, SAID ARCUATE SEGMENTS HAVING RADIALLY EXTENDING SOCKETS FOR RECEIVING THE TIPS OF THE BLADES IN A ROW OF ROTOR BLADES WITH THE TIPS OF THE BLADES BEING SLIDABLE LENGTHWISE OF THE SOCKETS, A SECOND PLURALITY OF ARCUATE SEGMENTS OUTBOARD OF THE BLADE TIPS AND LOCATED BETWEEN AND SPANNING THE FLANGES OF THE BLADE-RECEIVING SEGMENTS, THE SEGMENTS OF THE SECOND PLURALITY FORMING A RING, A RELATIVELY STIFF FILLER MEMBER IN THE SPACE BETWEEN THE SEGMENT RINGS AND SURROUNDING TIPS OF THE BLADES, AND A SUBSTANTIALLY CONTINUOUS WINDING OF RESIN-IMPREGNATED FILAMENTARY MATERIAL FORMING A RETAINING BAND EMBRACING THE SEGMENTS OF THE SECOND PLURALITY TO HOLD THE SEGMENTS TOGETHER. 